Buggy code:
public void addDocuments ( Iterable < ? extends Iterable < ? extends IndexableField > > docs ) throws IOException { } public void addDocuments ( Iterable < ? extends Iterable < ? extends IndexableField > > docs , Analyzer analyzer ) throws IOException { } public void updateDocuments ( Term delTerm , Iterable < ? extends Iterable < ? extends IndexableField > > docs ) throws IOException { } public void updateDocuments ( Term delTerm , Iterable < ? extends Iterable < ? extends IndexableField > > docs , Analyzer analyzer ) throws IOException { } public void deleteDocuments ( Term term ) throws IOException { } public synchronized boolean tryDeleteDocument ( IndexReader readerIn , int docID ) throws IOException { } public void deleteDocuments ( Term ... terms ) throws IOException { } public void deleteDocuments ( Query query ) throws IOException { } public void deleteDocuments ( Query ... queries ) throws IOException { } public void updateDocument ( Term term , Iterable < ? extends IndexableField > doc ) throws IOException { } public void updateDocument ( Term term , Iterable < ? extends IndexableField > doc , Analyzer analyzer ) throws IOException { } final synchronized int getSegmentCount ( ) { } final synchronized int getNumBufferedDocuments ( ) { } final synchronized Collection < String > getIndexFileNames ( ) throws IOException { } final synchronized int getDocCount ( int i ) { } final int getFlushCount ( ) { } final int getFlushDeletesCount ( ) { } final String newSegmentName ( ) { } final InfoStream infoStream ; public void forceMerge ( int maxNumSegments ) throws IOException { } public void forceMerge ( int maxNumSegments , boolean doWait ) throws IOException { } private synchronized boolean maxNumSegmentsMergesPending ( ) { } public void forceMergeDeletes ( boolean doWait ) throws IOException { } public void forceMergeDeletes ( ) throws IOException { } public final void maybeMerge ( ) throws IOException { } private final void maybeMerge ( MergeTrigger trigger , int maxNumSegments ) throws IOException { } private synchronized void updatePendingMerges ( MergeTrigger trigger , int maxNumSegments ) throws IOException { } public synchronized Collection < SegmentInfoPerCommit > getMergingSegments ( ) { } public synchronized OneMerge getNextMerge ( ) { } public synchronized boolean hasPendingMerges ( ) { } @ Override public void rollback ( ) throws IOException { } private void rollbackInternal ( ) throws IOException { } public void deleteAll ( ) throws IOException { } private synchronized void finishMerges ( boolean waitForMerges ) { } public synchronized void waitForMerges ( ) { } synchronized void checkpoint ( ) throws IOException { } synchronized void checkpointNoSIS ( ) throws IOException { } synchronized void changed ( ) { } synchronized void publishFrozenDeletes ( FrozenBufferedDeletes packet ) { } void publishFlushedSegment ( SegmentInfoPerCommit newSegment , FrozenBufferedDeletes packet , FrozenBufferedDeletes globalPacket ) throws IOException { } private synchronized void resetMergeExceptions ( ) { } private void noDupDirs ( Directory ... dirs ) { } public void addIndexes ( Directory ... dirs ) throws IOException { } public void addIndexes ( IndexReader ... readers ) throws IOException { } private SegmentInfoPerCommit copySegmentAsIs ( SegmentInfoPerCommit info , String segName , Map < String , String > dsNames , Set < String > dsFilesCopied , IOContext context , Set < String > copiedFiles ) throws IOException { } protected void doAfterFlush ( ) throws IOException { } protected void doBeforeFlush ( ) throws IOException { } @ Override public final void prepareCommit ( ) throws IOException { } private void prepareCommitInternal ( ) throws IOException { } public final synchronized void setCommitData ( Map < String , String > commitUserData ) { } public final synchronized Map < String , String > getCommitData ( ) { } private final Object commitLock = new Object ( ) ; @ Override public final void commit ( ) throws IOException { } public final boolean hasUncommittedChanges ( ) { <START_BUG> return ( changeCount ) != ( lastCommitChangeCount ) ; <END_BUG> } private final void commitInternal ( ) throws IOException { } private final synchronized void finishCommit ( ) throws IOException { } private final Object fullFlushLock = new Object ( ) ; boolean holdsFullFlushLock ( ) { } protected final void flush ( boolean triggerMerge , boolean applyAllDeletes ) throws IOException { } private boolean doFlush ( boolean applyAllDeletes ) throws IOException { } final synchronized void maybeApplyDeletes ( boolean applyAllDeletes ) throws IOException { } final synchronized void applyAllDeletes ( ) throws IOException { } public final long ramSizeInBytes ( ) { } DocumentsWriter getDocsWriter ( ) { } public final synchronized int numRamDocs ( ) { } private synchronized void ensureValidMerge ( MergePolicy . OneMerge merge ) { } private synchronized ReadersAndLiveDocs commitMergedDeletes ( MergePolicy . OneMerge merge , MergeState mergeState ) throws IOException { } private synchronized boolean commitMerge ( MergePolicy . OneMerge merge , MergeState mergeState ) throws IOException { } private final void handleMergeException ( Throwable t , MergePolicy . OneMerge merge ) throws IOException { } public void merge ( MergePolicy . OneMerge merge ) throws IOException { } void mergeSuccess ( MergePolicy . OneMerge merge ) { } final synchronized boolean registerMerge ( MergePolicy . OneMerge merge ) throws IOException { } final synchronized void mergeInit ( MergePolicy . OneMerge merge ) throws IOException { } private synchronized void _mergeInit ( MergePolicy . OneMerge merge ) throws IOException { } static void setDiagnostics ( SegmentInfo info , String source ) { } private static void setDiagnostics ( SegmentInfo info , String source , Map < String , String > details ) { } final synchronized void mergeFinish ( MergePolicy . OneMerge merge ) { } private final synchronized void closeMergeReaders ( MergePolicy . OneMerge merge , boolean suppressExceptions ) throws IOException { } private int mergeMiddle ( MergePolicy . OneMerge merge ) throws IOException { } synchronized void addMergeException ( MergePolicy . OneMerge merge ) { }

Fix:
return ( ( ( changeCount ) != ( lastCommitChangeCount ) ) || ( docWriter . anyChanges ( ) ) ) || ( bufferedDeletesStream . any ( ) ) ;